Rolling strip from powder

ABSTRACT

Apparatus for producing sheet and strip material, wherein particulate material is fed between a pair of opposed rolls and wherein a gauge is provided to sense the density of the rolled strip leaving the rolls and to provide a signal which is used in the control of the feed of particulate material to the rolls whereby rolled sheet and strip material of constant density is produced.

United States Patent Inventors George M. Sturgeon Dore; Geoffrey M. H. Sykes, Geecross Hyde, both of England Appl. No. 872,577

Filed Oct. 30, 1969 Patented Jan. 4, I972 Assignee The British Iron and Steel Research Association Priority Oct. 30, 1968 Great Britain 51,450/68 ROLLING STRIP FROM POWDER Primary ExaminerRobert L. Spicer, Jr. Attorney-Holcombe, Wetherill and Brisebois ABSTRACT: Apparatus for producing sheet and strip material, wherein particulate material is fed between a pair of opposed rolls and wherein a gauge is provided to sense the densi- 10 Claims, 2 Drawing Figs.

i ty of the rolled strip leaving the rolls and to provide a signal U-S. n v t e i i t l f p ti l t t i l 425/141 425/145 to the rolls whereby rolled sheet and strip material of constant Int. Cl B291! 7/14, density is produced POSITION 40 DEMODULAID? TRANSDUC R 7 78 SERVO BUFFER POWDER MOVING MOTOR AMPLIFIER I 32/3 JACK O O AMPL/HER E DEMOOULW 3 76 BUFFER mRauE PUMP8 MOVING 2/ 12 MOTOR S R 0 INT/GRA TING AMPLIFIER AMPLIFIER V5155 U UNIT 48 28 45 CONTACT STD GAUGE RIfSFERENCE T 1 7 STRIP IGNAL 14 Q ii/ a 7 l 143 42 0 T p MILL l BUFFER RATE AMPLIFIER COMPENSATIO 38 DEMOD T SET ROLL GAP CAL ROLLING STRIP FROM POWDER This invention relates to apparatus for producing sheet and strip from particulate material such as powder.

According to the invention there is provided apparatus for producing sheet and strip from particulate material, comprising a pair of opposed rolls defining a nip therebetween, means for adjusting the rate of feed of particulate material to the nip, means for producing a signal indicative of the density of the rolled sheet or strip leaving the rolls, and control means operable to control the feed-adjusting means in dependence of said signal whereby to maintain substantially constant the density of the rolled sheet or strip.

Features and advantages of the invention will be apparent from the following description of an embodiment thereof given, by way of example only, in conjunction with the accompanying drawing in which:

FIG. 1 shows diagrammatically the control system of a rolling mill according to the invention; and

FIG. 2 shows a modified feed arrangement for the mill of FIG. 1.

Referring to FIG. 1, the rolling mill generally includes a pair of opposed rolls 21, a hopper 22 for feeding powder 24 to the nip of the rolls, a system for controlling the density of the strip or sheet being rolled and a system 37 for maintaining a constant roll gap. The system 37 is very similar to that employed in our copending Great Britain application No. 28562/68 and corresponding US. application Ser. No. 832,571 and reference is made to these applications for a complete understanding of the operation of system 37; like parts in the accompanying drawing and FIG. 3 of 28562/68 are given the same reference numerals. Briefly, the system will operate to maintain a constant roll gap under load, i.e. the system makes adjustments in the roll setting to compensate for the elastic deformation of the various components of the roll stand. The embodiment shown uses a hydraulic jack 32 and a motor in the form of a servo valve and pump 28 to effect movement of the roll chocks, although screws and wedges actuated either hydraulically or by electric motors may also be used for this purpose. A control circuit including a variable resistor 38 provides a positive reference signal (R) to determine the required constant roll gap. The signal from a position transducer 51 indicates the extension (x) or the change in (x) of the jack, and the sense of this signal is negative, i.e. as the jack extends the transducer 51 gives a negative signal whose magnitude is proportional to the extension of the jack. Any proportion q of this signal can be fed into resistor 42 by suitable adjustment of a potentiometer 40. A pressure transducer 50 indicates the jack pressure (which is proportional to rolling load) and provides a positive signal proportional to the magnitude of the rolling load P. Any proportion r of this signal can be fed into a resistor 43 by adjustment of a potentiometer 45. An operational amplifier 46 and resistor 47 sums the signal fed into resistors 38, 42 and 43 and its output is given by Rqx+rP.

This error signal is fed into the servo valve, and if the signal has a positive sense the servo valve is operable to extend the jack, and vice versa; the jack will attain a steady state condition when the above error is zero, i.e. when If Y is the no load roll gap of the roll stand when the jack is fully extended (x=o), at any time under rolling load P, the actual roll gap Z will be given by Z=Yx+(P/M) (2) where M is the stiffness of the roll stand as a whole and the term P/M gives the elastic deflection of the stand.

Substituting for x from 1 If the values of r and q are selected such that q/r M, equation (3) is simplified to It can be seen that Z, the roll gap under load, is independent of the load and is constant when reference R is constant.

A roll gap control system such as that described in our British Patent Specification 692,267 and corresponding US. Pat. No. 2,680,978 may also be used.

System 10 includes a device 12, such as one or more gamma ray gauges, for producing a signal indicative of the density of the rolled product without physically contacting it; since the thickness of the product leaving the rolls 21 will be constant, the reading of device 12 will be directly related to the density of the rolled product.

To maintain substantially constant the density of the rolled product, an error signal, produced by combining the output signal of device 12 and standard reference signal 14 in an integrating unit 16, is fed to a servomotor 18, via amplifier 20. The motor 18 is operable to move each plate 22a relative to its respective roll so as to increase or decrease the area of the peripheral roll surface exposed to the particulate material in the hopper and thereby adjust the rate at which the powder enters the roll nip.

Alternatively, (see FIG. 2), the hopper 22 may be defined by plates 22b fixed relative to the rolls 21 and by the peripheral roll surfaces in the region of the roll nip; the servomotor 18 is operable to adjust the position of a tonguelike member 25 located in the hopper toward or away from the nip so as to adjust the amount of particulate material 24 fed to the nip.

It will be apparent from above that the described control v system of the rolling mill will have a fast response time, thus enabling accurate control of density and thickness of the rolled product.

In a modification of the above described apparatus, system 37 is omitted and the rolls 21 form part of an infinitely stiff rolling mill stand and are therefore settable to provide a desired roll gap which will remain substantially constant during rolling.

Since there is an interdependence between density and thickness, it will be apparent that adjustment of each plate 22a or member 25 to adjust density will normally also alter the thickness of the rolled product; however, by employing a constant roll gap system 37 or an infinitely still mill as described above it is possible to adjust the density of the rolled product without a corresponding change in gauge.

We claim:

1. Apparatus for producing sheet and strip from particulate material comprising,

a. a pair of opposed rolls defining a nip therebetween for rolling a sheet from particulate material,

b. feed-adjusting means for adjusting the rate of feed of the particulate material into the nip,

c. density-measuring means for measuring the density of the rolled sheet and producing a signal representative of the density,

d. spacing means operable to maintain a substantially constant spacing between the rolls, and

e. control means operable to control the feed-adjusting means in response to a signal representative of the density of the rolled sheet, to produce a sheet of substantially constant density and thickness.

2. Apparatus as claimed in claim 1 in which said spacing means comprises means for continuously measuring the spacing between the rolls and control means responsive to the output of said measuring means operative to maintain said spacing at a substantially constant value.

3. Apparatus according to claim 1 wherein the spacing means includes a jack permitting adjustment of the rolls toward or away from each other, a motor for effecting said adjustment, and a control circuit for feeding an error signal to the motor to maintain the roll gap constant, the control circuit being arranged so that the roll gap under load is independent of the load and is constant when a reference signal is constant.

4. Apparatus according to claim 1 wherein the rolls form part of an infinitely stiff rolling mill stand and are therefore settable to provide a desired roll gap which will remain substantially constant during rolling.

5. Apparatus according to claim 1 wherein the density-measuring means is operable to detect density of the rolled sheet without physically contacting it.

6. Apparatus according to claim 5 wherein the density-measuring means is a gamma ray gauge.

7. Apparatus according to claim 1 wherein the feed-adjusting means includes opposed plates one for each roll, defining together with the peripheral roll surfaces in the region of the nip a hopper for the particulate material, and wherein said control means is operable to move each plate relative to its respective roll so as to increase or decrease the area of the peripheral roll surface exposed to the particulate material in the hopper and thereby adjust the rate of the feed of the particulate material to the nip.

8. Apparatus according to claim 1 wherein said feed-adj usting means includes plates fixed relative to the rolls and defining together with the peripheral roll surfaces in the region of the nip a hopper for the particulate material, and a member positioned within the hopper and adjustable towards or away from the nip to adjust the amount of particulate material fed to the nip, and wherein said control means is operable to affect said adjustment of said member.

9. ln apparatus for producing sheet and strip including a pair of opposed rolls defining a nip therebetween for rolling from particulate material a sheet having a thickness determined by the spacing between said rolls, and feed means for feeding particulate material into said nip, the improvement which comprises in combination:

a. means for adjusting the rate of feed of said particulate material by said feed means,

b. density-measuring means for measuring the density of the rolled sheet and producing a signal representative of the density,

c. spacing means which maintains a substantially constant spacing between the rolls, and

(I. control means which controls the feed-adjusting means in response to a signal representative of the density of the rolled sheet to produce a sheet of substantially constant density and thickness.

10. Apparatus as claimed in claim 9 in which said spacing means comprises means for continuously measuring the spacing between the rolls and control means responsive to the output of said measuring means operative to maintain said spacing at a substantially constant value. 

1. Apparatus for producing sheet and strip from particulate material comprising, a. a pair of opposed rolls defining a nip therebetween for rolling a sheet from particulate material, b. feed-adjusting means for adjusting the rate of feed of the particulate material into the nip, c. density-measuring means for measuring the density of the rolled sheet and producing a signal representative of the density, d. spacIng means operable to maintain a substantially constant spacing between the rolls, and e. control means operable to control the feed-adjusting means in response to a signal representative of the density of the rolled sheet, to produce a sheet of substantially constant density and thickness.
 2. Apparatus as claimed in claim 1 in which said spacing means comprises means for continuously measuring the spacing between the rolls and control means responsive to the output of said measuring means operative to maintain said spacing at a substantially constant value.
 3. Apparatus according to claim 1 wherein the spacing means includes a jack permitting adjustment of the rolls toward or away from each other, a motor for effecting said adjustment, and a control circuit for feeding an error signal to the motor to maintain the roll gap constant, the control circuit being arranged so that the roll gap under load is independent of the load and is constant when a reference signal is constant.
 4. Apparatus according to claim 1 wherein the rolls form part of an infinitely stiff rolling mill stand and are therefore settable to provide a desired roll gap which will remain substantially constant during rolling.
 5. Apparatus according to claim 1 wherein the density-measuring means is operable to detect density of the rolled sheet without physically contacting it.
 6. Apparatus according to claim 5 wherein the density-measuring means is a gamma ray gauge.
 7. Apparatus according to claim 1 wherein the feed-adjusting means includes opposed plates one for each roll, defining together with the peripheral roll surfaces in the region of the nip a hopper for the particulate material, and wherein said control means is operable to move each plate relative to its respective roll so as to increase or decrease the area of the peripheral roll surface exposed to the particulate material in the hopper and thereby adjust the rate of the feed of the particulate material to the nip.
 8. Apparatus according to claim 1 wherein said feed-adjusting means includes plates fixed relative to the rolls and defining together with the peripheral roll surfaces in the region of the nip a hopper for the particulate material, and a member positioned within the hopper and adjustable towards or away from the nip to adjust the amount of particulate material fed to the nip, and wherein said control means is operable to affect said adjustment of said member.
 9. In apparatus for producing sheet and strip including a pair of opposed rolls defining a nip therebetween for rolling from particulate material a sheet having a thickness determined by the spacing between said rolls, and feed means for feeding particulate material into said nip, the improvement which comprises in combination: a. means for adjusting the rate of feed of said particulate material by said feed means, b. density-measuring means for measuring the density of the rolled sheet and producing a signal representative of the density, c. spacing means which maintains a substantially constant spacing between the rolls, and d. control means which controls the feed-adjusting means in response to a signal representative of the density of the rolled sheet to produce a sheet of substantially constant density and thickness.
 10. Apparatus as claimed in claim 9 in which said spacing means comprises means for continuously measuring the spacing between the rolls and control means responsive to the output of said measuring means operative to maintain said spacing at a substantially constant value. 